Electrophysiology catheters are commonly-used for mapping electrical activity in the heart. Various electrode designs are known for different purposes. In particular, catheters having basket-shaped electrode arrays are known and described, for example, in U.S. Pat. Nos. 5,772,590, 6,748,255 and 6,973,340, the entire disclosures of both of which are incorporated herein by reference.
Basket catheters typically have an elongated catheter body and a basket-shaped electrode assembly mounted at the distal end of the catheter body. The basket assembly has proximal and distal ends and comprises a plurality of spines connected at their proximal and distal ends. Each spine comprises at least one electrode. The basket assembly has an expanded arrangement wherein the spines bow radially outwardly and a collapsed arrangement wherein the spines are arranged generally along the axis of the catheter body. The catheter may further comprise a distal location sensor mounted at or near the distal end of the basket-shaped electrode assembly and a proximal location sensor mounted at or near the proximal end of the basket-shaped electrode assembly. In use, the coordinates of the distal location sensor relative to those of the proximal sensor can be determined and taken together with known information pertaining to the curvature of the spines of the basket-shaped mapping assembly to find the positions of the at least one electrode of each spine.
A basket assembly is capable of detecting in a single beat most or all of the electrical function of the left or right atrium. However, because the atria of an individual patient may vary in size and shape, it is desirable that the basket assembly be sufficiently versatile and steerable to conform to the particular atrium. A basket catheter with a deflectable basket assembly for improved maneuverability to provide better tissue contact, especially in a cavernous region of the heart, including an atrium, is described in U.S. application Ser. No. 14/028,435, filed Sep. 16, 2013, the entire disclosure of which is hereby incorporated by reference.
High-density microelectrodes are also desirable for providing greater sensitivity in detecting more subtle electrical activity of heart tissue in diagnosing arrhythmias. By having a large number of electrodes often in a basket formation with spines of spaced ring electrodes, a physician can more quickly map a large area of the heart's interior geometry. Focal catheters, although lacking the resolution of a basket catheter with many electrodes, can be advantageous because their electrode location is fixed relative to the catheter distal tip.
Accordingly, it is also desirable that a basket catheter provide high-density mapping augmented with a focal diagnostic catheter tip with precisely known microelectrode locations, especially where the focal tip electrode is populated with an array of microelectrodes, in a focal catheter dimensional envelope, or even smaller, such as within a guidewire range.